JP2017141726A - Internal combustion engine, device and method for controlling the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine which can suppress knocking and reduce a consumption of a high octane number fuel.SOLUTION: A fuel is stored in a first fuel tank 22 provided on an internal combustion engine 1, and a high octane number fuel is stored in a second fuel tank 44. Water is stored in a water tank 40. A first fuel injection valve 21 injects the fuel supplied from the first fuel tank 22 into a combustion chamber 14. A second fuel injection valve 52 injects a liquid mixture, in which the high octane number fuel supplied from the second fuel tank 44 and the water supplied from the water tank 40 are mixed, into an intake passage 32. The liquid mixture, because the boiling point is lower than water due to azeotropy, evaporates in a short time and therefore can sufficiently cool the inside of a cylinder even in warming-up operation or in a high rotation.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an internal combustion engine, a control device and a control method thereof.

Conventionally, various techniques capable of suppressing knocking of an internal combustion engine are known.
For example, the internal combustion engine described in Patent Document 1 operates using gasoline as a low octane fuel and ethanol as a high octane fuel to suppress knocking. When the output torque required for the internal combustion engine increases, the internal combustion engine increases the amount of air supplied into the cylinder and controls to increase the ratio of the high octane fuel to the low octane fuel. On the other hand, when the output torque required for the internal combustion engine decreases, the amount of air supplied into the cylinder is reduced, the ratio of the high octane number fuel to the low octane number fuel is reduced, and the amount of air supplied into the cylinder is reduced. Exhaust gas recirculation (EGR) control is performed to increase the amount of gas. As a result, this internal combustion engine suppresses knocking of the internal combustion engine and suppresses the consumption of high octane fuel.

JP2012-163002A

However, the technique described in Patent Document 1 has the following problems.
First, this technique only increases the EGR gas and reduces the consumption of high-octane fuel only when the output torque required for the internal combustion engine decreases. When the output torque required for the internal combustion engine increases, control is performed to increase the proportion of high octane fuel. Therefore, with this technology, if the operation is continued for a long time, the high-octane fuel may be exhausted.

  Second, this technique suppresses knocking only by increasing the EGR gas if the high-octane fuel is depleted. Therefore, with this technique, there is a concern that knocking of the internal combustion engine cannot be sufficiently suppressed when high octane fuel is exhausted.

  The present invention has been made in view of the above points, and an object of the present invention is to provide an internal combustion engine capable of suppressing knocking and reducing the consumption of high-octane fuel, and a control device and control method therefor. And

  An internal combustion engine of a first invention includes an engine body, a spark plug, an intake system, an exhaust system, a first fuel tank, a first fuel injection valve, a second fuel tank, a water tank, and a second fuel injection valve. In the combustion chamber formed in the engine body, the spark plug discharges with a spark. The intake system introduces air into the combustion chamber through the intake passage. The exhaust system exhausts exhaust from the combustion chamber through the exhaust passage. The first fuel tank stores fuel. The first fuel injection valve injects fuel supplied from the first fuel tank into the intake passage or the combustion chamber. The second fuel tank stores high-octane fuel having a higher octane number than the fuel stored in the first fuel tank. The water tank stores water. The second fuel injection valve injects a mixed liquid obtained by mixing high octane fuel supplied from the second fuel tank and water supplied from the water tank into the intake passage or the combustion chamber.

As a result, when knocking occurs, the internal combustion engine of the first invention injects a mixed liquid obtained by mixing high-octane fuel and water from the second fuel injection valve in addition to the fuel injected from the first fuel injection valve. Is possible. Since the boiling point of the mixed liquid is lower than that of water due to azeotropy, it is vaporized in a short time. Therefore, the internal combustion engine can cool the inside of the cylinder by the latent heat of vaporization of the mixed liquid and suppress knocking even during the warm-up operation or during the high rotation, in addition to after the warm-up and during the low rotation.
Moreover, since this internal combustion engine injects the liquid mixture which mixed the high octane fuel and water from the 2nd fuel injection valve, it is possible to reduce the consumption of the high octane fuel. Therefore, this internal combustion engine can maintain the knocking suppression effect during long-time operation.

The second invention is an invention of a control device for an internal combustion engine. The control device is configured to perform fuel injection from the first fuel injection valve when knocking of the internal combustion engine is detected by an output signal of a knock sensor that detects vibration of the engine body or an in-cylinder pressure sensor that detects in-cylinder pressure. In addition, control is performed to inject a mixed liquid obtained by mixing high octane fuel and water from the second fuel injection valve.
Thereby, the 2nd invention can have the same operation effect as the 1st invention.

  The third invention is an invention of a control method for an internal combustion engine. This control method includes a knock determination step, a warm-up determination step, a mixed liquid increase step, and a high octane fuel increase step. In the knock determination step, it is determined whether the output signal of the knock sensor that detects the vibration of the engine body or the output signal of the in-cylinder pressure sensor that detects the in-cylinder pressure is greater than a first threshold value. In the warm-up determination step, it is determined whether or not the temperature of the internal combustion engine is greater than a second threshold value. In the mixed liquid increasing step, when the output signal of the knock sensor or the output signal of the in-cylinder pressure sensor is larger than the first threshold value and the temperature of the internal combustion engine is larger than the second threshold value, injection of the mixed liquid of high octane fuel and water Increase the amount. In the high octane number fuel increasing step, when the output signal of the knock sensor or the output signal of the in-cylinder pressure sensor is larger than the first threshold value and the temperature of the internal combustion engine is smaller than the second threshold value, the amount of the high octane number fuel contained in the liquid mixture Increase the amount.

  Thereby, in the control method of the third invention, when the warm-up is sufficiently performed, the injection amount of the mixed liquid can be increased, the inside of the cylinder can be cooled, and knocking can be suppressed. Further, when the warm-up is not sufficiently performed, the amount of high octane fuel can be increased, and the ignition temperature of the fuel can be increased to suppress knocking.

The block diagram of the internal combustion engine by 1st Embodiment of this invention. The map which shows the relationship between the driving | running state of the internal combustion engine by 1st Embodiment, and injected fuel. The map which shows the relationship between the driving | running state of an internal combustion engine and the injection fuel at the time of the residual amount reduction of a high octane number fuel. The flowchart of the fuel-injection control of the internal combustion engine by 1st Embodiment. The flowchart of the fuel injection control of the internal combustion engine by 2nd Embodiment.

Hereinafter, a plurality of embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
A first embodiment of the present invention is shown in FIGS. The internal combustion engine 1 of this embodiment is a multi-cylinder or single-cylinder gasoline spark ignition internal combustion engine.
First, the configuration of the internal combustion engine 1 will be described with reference to FIG. The internal combustion engine 1 includes an engine body 2, an intake system 3, an exhaust system 4, an EGR device 5, a rainwater collector 6, a stirrer 7, a control device (ECU) 8, and the like.

  The engine body 2 includes a cylinder block 9 having a cylindrical cylinder, a cylinder head 10 that forms a ceiling of the cylinder, and the like. Inside the cylinder, a piston 11, a connecting rod 12, a crankshaft 13, and the like are housed. Inside the engine body 2, a combustion chamber 14 is formed by the inner walls of the cylinder block 9 and the cylinder head 10 and the upper end surface of the piston 11. The cylinder block 9 is provided with a temperature sensor 15 that detects the temperature of the cooling water. A knock sensor 16 for detecting vibration of the engine body 2 is attached to the outer wall of the cylinder block 9.

The cylinder head 10 is provided with an ignition plug 17 for spark discharge in the combustion chamber 14 and an in-cylinder pressure sensor 18 for detecting the in-cylinder pressure. The ignition coil 19 electrically connected to the spark plug 17 converts a battery voltage (not shown) into a high voltage necessary for discharging the spark plug 17.
The piston 11 can reciprocate in the axial direction inside the cylinder. The reciprocating motion of the piston 11 is converted into the rotational motion of the crankshaft 13 via the connecting rod 12. The rotation angle of the crankshaft 13 is detected by a crank angle sensor 20.

  The cylinder head 10 is provided with a first fuel injection valve 21. The first fuel tank 22 connected to the first fuel injection valve 21 stores gasoline as fuel. The first fuel injection valve 21 is supplied with fuel pumped up from a first fuel tank 22 by a pump (not shown). The first fuel injection valve 21 directly injects and supplies the fuel supplied from the first fuel tank 22 into the cylinder.

  The cylinder head 10 has an intake port 23 and an exhaust port 24. The intake valve 25 opens and closes an opening where the intake port 23 opens into the combustion chamber 14, and the exhaust valve 26 opens and closes an opening where the exhaust port 24 opens into the combustion chamber 14. The intake valve opening / closing mechanism 27 that drives the intake valve 25 is constituted by a camshaft or the like that rotates by torque transmission from the crankshaft 13. The exhaust valve opening / closing mechanism 28 for driving the exhaust valve 26 is also constituted by another camshaft or the like that rotates by torque transmission from the crankshaft 13.

The intake system 3 includes an intake pipe 29, an air cleaner 30, a throttle 31, and an intake port 23. In the intake stroke of the internal combustion engine 1, when the piston 11 moves from the top dead center toward the bottom dead center, air is introduced into the combustion chamber 14 through the intake passage 32 formed in the intake pipe 29 and the like. The air cleaner 30 removes foreign matters in the air. The throttle 31 adjusts the amount of air introduced into the combustion chamber 14. A flow meter 33 for detecting the amount of air introduced into the combustion chamber 14 is attached to the intake passage 32 in the air cleaner 30.
The exhaust system 4 includes an exhaust pipe 34 and the like. In the exhaust stroke of the internal combustion engine 1, when the piston 11 moves from the bottom dead center toward the top dead center, the exhaust is discharged from the combustion chamber 14 through the exhaust passage 35 formed in the exhaust pipe 34 or the like.

  The EGR device 5 includes an EGR passage 36, an EGR valve 37, an EGR cooler 38, and the like. The EGR passage 36 connects the exhaust passage 35 and the intake passage 32, and returns a part of the exhaust gas flowing through the exhaust passage 35 to the intake passage 32. The EGR valve 37 is provided in the EGR passage 36 and adjusts the amount of exhaust flowing through the EGR passage 36. The EGR cooler 38 is configured by, for example, a heat exchanger through which cooling water flows, and cools the exhaust gas flowing through the EGR passage 36.

The EGR cooler 38 is connected to the water tank 40 via a condensed water pipe 39. The condensed water pipe 39 is provided with a check valve 41 that allows water flow from the EGR cooler 38 to the water tank 40 and blocks water flow from the water tank 40 to the EGR cooler 38. Thereby, the water condensed from the exhaust gas passing through the heat exchanger of the EGR cooler 38 passes through the condensed water pipe 39 and is stored in the water tank 40. A neutralizing agent (not shown) for neutralizing the condensed water of the EGR cooler 38 may be attached to the EGR cooler 38, the condensed water pipe 39 or the water tank 40.
The water tank 40 is connected to a rainwater collector 6 that collects rainwater via a rainwater pipe 42. Thereby, the water collected by the rainwater collector 6 passes through the rainwater pipe 42 and is stored in the water tank 40. The water tank 40 is provided with a water remaining amount meter 43 that detects the remaining amount of water stored in the water tank 40.

  On the other hand, the second fuel tank 44 stores high-octane fuel having a higher octane number than the fuel stored in the first fuel tank 22. Ethanol is exemplified as the high octane fuel. The second fuel tank 44 is provided with a high octane fuel remaining amount meter 45 that detects the remaining amount of high octane fuel stored in the second fuel tank 44.

  The water tank 40 is connected to the stirrer 7 through a water pipe 46, and the second fuel tank 44 is also connected to the stirrer 7 through a fuel pipe 47. The water pipe 46 is provided with a water supply valve 48 for adjusting the amount of water supplied from the water tank 40 to the stirrer 7. The fuel pipe 47 is provided with a high octane fuel supply valve 49 for adjusting the amount of high octane fuel supplied from the second fuel tank 44 to the agitator 7.

  The stirrer 7 stirs the high octane fuel and water by the rotation of the stirring blade 50 to form a mixed solution. The stirrer 7 is provided with a concentration sensor 51 for detecting the concentration of high octane fuel or water in the mixed solution. The liquid mixture generated by the stirrer 7 is supplied to the second fuel injection valve 52. The second fuel injection valve 52 injects and supplies the liquid mixture supplied from the stirrer 7 to the intake port 23.

  The ECU 8 is a computer having a CPU, a RAM, a ROM, and the like. The ECU 8 outputs the temperature sensor 15, knock sensor 16, in-cylinder pressure sensor 18, crank angle sensor 20, flow meter 33, concentration sensor 51, water remaining amount meter 43, high octane fuel amount remaining amount meter 45, and the like. A signal is input. In addition, the ECU 8 includes various parts of the internal combustion engine 1 such as the ignition plug 17, the first fuel injection valve 21, the second fuel injection valve 52, the throttle 31, the EGR valve 37, the water supply valve 48, the high octane fuel supply valve 49, and the like. To control.

By the way, in general, in a gasoline spark ignition type internal combustion engine, when the load becomes high and the amount of intake air increases, the compression ratio increases, and the unburned mixture (end gas) located far from the spark plug 17 becomes the inner wall of the cylinder. It becomes high temperature and high pressure by adiabatic compression. When the end gas self-ignites all at once and burns rapidly, the pressure in the combustion chamber 14 rapidly rises and a shock wave is generated. Thereby, knocking occurs.
The ECU 8 can detect whether knocking has occurred in the internal combustion engine 1 based on the output signal of the knock sensor 16 or the output signal of the in-cylinder pressure sensor 18 described above.

Next, fuel injection control performed by the ECU 8 of the present embodiment for suppressing knocking will be described with reference to the maps of FIGS.
FIG. 2 shows the relationship between the operating state of the internal combustion engine and the injected fuel when the second fuel tank 44 has a sufficient amount of high octane fuel. The remaining amount of high octane fuel can be detected by the output signal of the high octane fuel remaining meter 45 attached to the second fuel tank 44.

In FIG. 2, dots are attached to the operation region where knocking occurs. In the following description, an operation region in which knocking does not occur is referred to as “normal region A”, and an operation region in which knocking may occur is referred to as “knock occurrence region B”.
In the knock generation region B, the ECU 8 according to the present embodiment performs control to inject a mixed liquid obtained by mixing high-octane fuel and water from the second fuel injection valve 52 in addition to the fuel injection from the first fuel injection valve 21. Is. Specifically, when the ECU 8 detects knocking of the internal combustion engine 1 based on the output signal of the knock sensor 16 or the in-cylinder pressure sensor 18, the ECU 8 continues to inject fuel from the first fuel injection valve 21 and performs second fuel injection. The mixed liquid is injected from the valve 52. Since the liquid mixture injected from the second fuel injection valve 52 has a boiling point lower than that of water due to azeotropy, it is vaporized in the cylinder in a short time. Thereby, the inside of a cylinder is cooled by the vaporization latent heat of a liquid mixture, and knocking is suppressed.

Further, the ECU 8 increases the injection amount of the liquid mixture injected from the second fuel injection valve 52 as the knocking state detected by the output signal of the knock sensor 16 or the in-cylinder pressure sensor 18 increases, or the liquid mixture Increase the ratio of water to high octane fuel at
Further, the ECU 8 increases the injection amount of the mixed liquid injected from the second fuel injection valve 52 as the high load region, that is, the intake air amount increases, or sets the ratio of water to the high octane fuel in the mixed liquid. May increase.

  The ECU 8 adjusts the opening degree of the water supply valve 48 and the opening degree of the high octane fuel supply valve 49 based on the output signal of the concentration sensor 51 provided in the stirrer 7. Thus, the amount of water supplied from the water tank 40 to the stirrer 7 and the amount of high octane fuel supplied from the second fuel tank 44 to the stirrer 7 are adjusted. Therefore, the ratio of the high octane fuel and water in the mixed liquid supplied from the stirrer 7 to the second fuel injection valve 52 is adjusted.

Further, the ECU 8 detects the warm-up state or the cold state of the internal combustion engine 1 based on the output signal of the temperature sensor 15. When the internal combustion engine 1 is in a warm-up state or in a warm-up operation, the ECU 8 performs control to inject a mixed liquid of high octane fuel and water from the second fuel injection valve 52 as described above.
On the other hand, when the internal combustion engine 1 is in the cold state or the initial state of the warm-up operation, the ECU 8 performs control to inject only the high-octane fuel from the second fuel injection valve 52 instead of the liquid mixture. This is because when the internal combustion engine 1 is in the cold state or the initial state of the warm-up operation, it takes time to vaporize the liquid mixture, thereby preventing the combustion from deteriorating.

  FIG. 2 shows the relationship between the operating state of the internal combustion engine and the injected fuel when the second fuel tank 44 has a sufficient amount of high-octane fuel. On the other hand, FIG. 3 shows the relationship between the operating state of the internal combustion engine and the injected fuel when the remaining amount of high octane fuel in the second fuel tank 44 is reduced or exhausted. In FIG. 3, the “knocking occurrence region B” is hatched in an operation region having a rotational speed lower than a predetermined rotational speed. In the following description, the operation region is referred to as “low rotation high load region C”.

  The ECU 8 can detect the remaining amount of the high octane fuel stored in the second fuel tank 44 based on the output signal of the high octane fuel remaining amount meter 45 provided in the second fuel tank 44. The ECU 8 performs the following control when the remaining amount of high-octane fuel stored in the second fuel tank 44 becomes a predetermined amount or less. That is, when the internal combustion engine 1 is in a warm-up state and the operation state of the internal combustion engine 1 is in the low rotation high load region C, the ECU 8 changes only the water from the second fuel injection valve 52 to the mixed liquid. Control to inject. When the rotational speed of the internal combustion engine 1 is low, since the time from the time when the second fuel injection valve 52 injects water to the time when the ignition plug 17 is ignited is relatively long, water and air are agitated and water is vaporized. This is because it is performed sufficiently.

Subsequently, a control method performed by the ECU 8 of the present embodiment will be described with reference to a flowchart of FIG.
First, in the knock determination step (S101), the ECU 8 determines whether or not the output signal of the knock sensor 16 is greater than a predetermined threshold value (α). When the output signal is larger than the predetermined threshold value (α), it is assumed that knocking has occurred in the internal combustion engine 1, and the process proceeds to the injection amount limit determination step (S102).
On the other hand, when the output signal is smaller than the predetermined threshold value (α), the process continues the knock determination step (S101).
The predetermined threshold (α) corresponds to an example of a first threshold described in the claims.

In the injection amount limit determination step (S102), first, the injection amount of high octane fuel contained in the mixture injected from the second fuel injection valve 52 with respect to the injection amount of fuel injected from the first fuel injection valve 21. Calculate the percentage of. Next, it is determined whether or not the ratio of the injection amount of the high octane fuel is larger than a predetermined threshold (β). This is because if the ratio is larger than the predetermined threshold (β), the ignitability of the fuel may be deteriorated.
If the mixed liquid is not injected from the second fuel injection valve 52, the ratio of the injection amount of the high octane fuel is usually smaller than the predetermined threshold value (β), so the processing is the warm-up determination step (S103). Migrate to

In the warm-up determination step (S103), the ECU 8 determines whether or not the output signal of the temperature sensor 15 is greater than a predetermined threshold value (γ). When the output signal is larger than the predetermined threshold value (γ), it is determined that the internal combustion engine 1 is in the warm-up state or in the warm-up operation, and the process proceeds to the mixed liquid increasing step (S104).
The predetermined threshold (γ) corresponds to an example of a second threshold described in the claims.
In the mixed liquid increasing step (S104), the ECU 8 performs control to increase the injection amount of the mixed liquid of high octane fuel and water injected from the second fuel injection valve 52 by a predetermined amount. Thereafter, the process proceeds to the first knock determination step (S101), and the above-described process is repeatedly executed.

  On the other hand, if it is determined in the warm-up determination step (S103) that the output signal of the temperature sensor 15 is smaller than the predetermined threshold value (γ), the internal combustion engine 1 is assumed to be in the cold state or the initial state of the warm-up operation. The process proceeds to a high octane fuel increase step (S105). In the high octane fuel increase step (S105), control is performed to increase the injection amount of the high octane fuel contained in the mixed liquid by a predetermined amount. Thereafter, the process proceeds to the first knock determination step (S101), and the above-described process is repeatedly executed.

  When the above-described processing is repeatedly performed, in the injection amount limit determination step (S102), the ratio of the injection amount of high octane fuel contained in the liquid mixture injected from the second fuel injection valve 52 is a predetermined threshold value ( When larger than β), the process repeats the knock determination step (S101) and the injection amount limit determination step (S102). Thereby, it is prohibited that the ratio of the injection amount of the high octane fuel contained in the mixed liquid injected from the second fuel injection valve 52 is further increased. That is, in the injection amount limit determination step (S102), the process (S102; YES) for determining that the ratio of the injection amount of the high-octane fuel contained in the mixed liquid is greater than the predetermined threshold (β) (S102: YES) This corresponds to an example of the “high octane fuel increase prohibition step” described in 1.

The internal combustion engine 1 of the present embodiment has the following operational effects.
(1) When knocking occurs, the internal combustion engine 1 of the present embodiment uses a mixed liquid obtained by mixing high octane fuel and water from the second fuel injection valve 52 in addition to the fuel injected from the first fuel injection valve 21. Spray. Since the boiling point of the mixed solution is lower than that of water due to azeotropy, the mixture is vaporized in a short time. Therefore, the internal combustion engine 1 can cool the inside of the cylinder by the latent heat of vaporization of the liquid mixture and suppress knocking even during warm-up operation or during high rotation, in addition to after warm-up and during low rotation.
Further, since the internal combustion engine 1 injects a mixed liquid obtained by mixing high octane fuel and water from the second fuel injection valve 52, it is possible to reduce consumption of the high octane fuel. Therefore, this internal combustion engine can maintain the knocking suppression effect during long-time operation.
Further, the internal combustion engine 1 injects the mixed liquid from the second fuel injection valve 52 into the intake passage 32. For this reason, the mixed liquid is introduced into the combustion chamber 14 from the intake passage 32 and is sufficiently agitated with the air to be vaporized, so that the entire combustion chamber 14 can be uniformly cooled.

(2) In the internal combustion engine 1 of the present embodiment, water condensed from the exhaust gas passing through the EGR cooler 38 is supplied to the water tank 40.
Thereby, since water is always replenished to the water tank 40 during the operation of the internal combustion engine 1, it is possible to prevent the water in the water tank 40 from being depleted. Therefore, this internal combustion engine can maintain the knocking suppression effect during long-time operation.

(3) In the internal combustion engine 1 of the present embodiment, the water collected by the rainwater collector 6 is supplied to the water tank 40.
Thereby, since water is replenished to the water tank 40 at the time of rain, it can suppress that the water in the water tank 40 is exhausted. The number of times that the driver or the like replenishes the water tank 40 can be reduced.

(4) The internal combustion engine 1 of the present embodiment mixes the high octane fuel supplied from the second fuel tank 44 and the water supplied from the water tank 40 by the stirrer 7. The ECU 8 supplies the amount of high octane fuel supplied from the second fuel tank 44 to the stirrer 7 and the water tank 40 to the stirrer 7 based on the output signal of the concentration sensor 51 that detects the concentration of the mixed liquid. Adjust the amount of water.
Thereby, it is possible to adjust the concentration of the high octane fuel and water in the mixed liquid injected from the second fuel injection valve 52.
Further, the high-octane fuel and water can be uniformly mixed by the stirrer 7.

The ECU 8 provided in the internal combustion engine 1 of the present embodiment has the following operational effects.
(5) The ECU 8 of the present embodiment performs control for injecting the liquid mixture from the second fuel injection valve 52 in addition to the fuel injection from the first fuel injection valve 21 when knocking of the internal combustion engine 1 is detected. It is.
Thereby, when knocking occurs, the ECU 8 can cool the inside of the cylinder by the vaporization latent heat of the mixed liquid and suppress knocking.

(6) The ECU 8 of the present embodiment increases the injection amount of the liquid mixture injected from the second fuel injection valve 52 or increases the proportion of water in the liquid mixture as the knocking of the internal combustion engine 1 increases.
Thereby, ECU8 can adjust the injection amount of a liquid mixture or the ratio of the water in a liquid mixture according to the magnitude | size of knocking, and can suppress knocking reliably.

(7) When the internal combustion engine 1 is in a warm-up state, the ECU 8 of the present embodiment performs control to inject a mixed liquid of high octane fuel and water. On the other hand, when the internal combustion engine 1 is in a cold state, the ECU 8 performs control to inject high octane fuel instead of the mixed liquid.
Thereby, when the internal combustion engine 1 is in a cold state, it is possible to prevent the water contained in the liquid mixture from being sufficiently vaporized.

(8) The ECU 8 of the present embodiment replaces the mixed liquid when the internal combustion engine 1 is in a warm-up state and the remaining amount of the high octane fuel stored in the second fuel tank 44 becomes a predetermined amount or less. Control to inject water.
As a result, knocking can be suppressed even when the remaining amount of high-octane fuel becomes zero or close to it.

(9) The ECU 8 of the present embodiment performs control for injecting water instead of the mixed liquid when the internal combustion engine 1 is in a warm-up state and the operation state of the internal combustion engine 1 is in the low rotation high load region. Do.
When the operating state of the internal combustion engine 1 is low, the time from the injection time of the second fuel injection valve 52 to the ignition time of the spark plug 17 is relatively long as compared with the case of high rotation. Therefore, the water injected from the second fuel injection valve 52 is sufficiently vaporized by being stirred with air. Therefore, the ECU 8 can suppress knocking by injecting only water from the second fuel injection valve 52.

The control method of the internal combustion engine 1 of the present embodiment has the following operational effects.
(10) In the control method of the present embodiment, when the temperature of the internal combustion engine 1 is higher than the predetermined threshold value (γ), a process of increasing the injection amount of the mixed liquid of high octane fuel and water is performed. On the other hand, when the temperature of the internal combustion engine 1 is smaller than a predetermined threshold value (γ), a process for increasing the amount of high octane fuel contained in the mixed liquid is performed.
Therefore, in this control method, when the warm-up is sufficient, the injection amount of the mixed liquid can be increased, and the inside of the cylinder can be cooled to suppress knocking. Further, when the warm-up is not sufficiently performed, the amount of high octane fuel can be increased, and the ignition temperature of the fuel can be increased to suppress knocking.

(11) In the control method of the present embodiment, the amount of high octane fuel contained in the mixture injected from the second fuel injection valve 52 is predetermined with respect to the injection amount of fuel injected from the first fuel injection valve 21. (S102; YES), the increase in high octane fuel is prohibited.
Thereby, it can prevent that the ignitability of a fuel deteriorates because the quantity of high octane fuel increases.

(Second Embodiment)
FIG. 5 shows a flowchart relating to a method for controlling the internal combustion engine 1 according to the second embodiment of the present invention. In the second embodiment, in the knock determination step (S201), the ECU 8 determines whether or not the output signal of the in-cylinder pressure sensor 18 is greater than a predetermined threshold value (δ). When the output signal is larger than the predetermined threshold value (δ), it is assumed that knocking has occurred in the internal combustion engine 1, and the process proceeds to the injection amount limit determination step (S202).
On the other hand, when the output signal is smaller than the predetermined threshold value (δ), the process continues the knock determination step (S201).
The predetermined threshold value (δ) corresponds to an example of a first threshold value described in the claims.

The injection amount limit determination step (S202), warm-up determination step (S203), mixed liquid increase step (S204), and high octane fuel increase step (S205) of the second embodiment are the same as those described in the first embodiment (S102). , S103, S104, S105).
However, in the second embodiment, after the mixed liquid increasing step (S204), the process proceeds to the combustion fluctuation determining step (S206). In the combustion fluctuation determination step (S206), it is determined whether or not the combustion fluctuation rate is smaller than a predetermined threshold value (η). The combustion fluctuation rate is a value obtained by dividing the standard deviation of the in-cylinder pressure in the combustion cycle in the predetermined period of the internal combustion engine 1 by the average value of the in-cylinder pressure in the combustion cycle in the predetermined period. If it is determined that the combustion fluctuation rate is smaller than the predetermined threshold value (η), the process proceeds to the water amount increasing step (S207) assuming that the combustion in the combustion cycle of the predetermined period is stable.
The predetermined threshold (η) corresponds to an example of a third threshold described in the claims.

  In the water amount increasing step (S207), the injection amount of the mixed liquid injected from the second fuel injection valve 52 is increased, or the ratio of water to the high octane fuel in the mixed liquid is increased. Thereby, the inside of a cylinder is further cooled and knocking is suppressed. Thereafter, the process proceeds to the first knock determination step (S201), and the above-described process is repeatedly executed.

  On the other hand, in the combustion fluctuation determination step (S206), if it is determined that the combustion fluctuation rate is greater than the predetermined threshold (η), without increasing the injection amount of the liquid mixture or increasing the concentration of water in the liquid mixture, The process proceeds to the first knock determination step (S201), and the above-described process is repeatedly executed. Thereby, it is prohibited that the ratio of the injection amount of water contained in the mixed liquid injected from the second fuel injection valve 52 further increases. That is, in the combustion fluctuation determination step (S206), the process (S206; YES) for determining that the combustion fluctuation rate is larger than the predetermined threshold (η) is an example of the “water volume increase prohibiting step” described in the claims. Equivalent to.

In the control method of the internal combustion engine 1 according to the second embodiment, when the combustion fluctuation rate is smaller than the predetermined threshold (η), the injection amount of the liquid mixture injected from the second fuel injection valve 52 is increased, or the liquid mixture Increase the ratio of water to high octane fuel at On the other hand, when the combustion fluctuation rate is larger than a predetermined threshold value (η), an increase in the injection amount of the liquid mixture injected from the second fuel injection valve 52 is prohibited, or an increase in the concentration of water in the liquid mixture is prohibited. .
Thereby, it is possible to prevent deterioration of combustion due to water injection from the second fuel injection valve 52.

(Other embodiments)
(1) In the above-described embodiment, the first fuel injection valve 21 is configured to directly inject and supply fuel into the cylinder. On the other hand, in another embodiment, the first fuel injection valve 21 may be configured to inject fuel into the intake passage 32.

(2) In the above-described embodiment, the second fuel injection valve 52 is configured to inject and supply the mixed liquid to the intake passage 32. On the other hand, in another embodiment, the second fuel injection valve 52 may be configured to directly inject and supply the mixed liquid into the cylinder. In this case, it is preferable that the second fuel injection valve 52 is attached to the center of the cylinder head 10 to cool the entire cylinder.

(3) In the above-described embodiment, the ECU 8 performs the first knock determination step (S101, S201) after performing the control to increase the injection amount of the mixed liquid by a predetermined amount in the mixed liquid increase step (S104, S204). The control to increase the injection amount of the mixed liquid by a predetermined amount is repeatedly performed. In addition, after the control to increase the injection amount of the high octane fuel contained in the mixed liquid by a predetermined amount in the high octane fuel increase step (S105, S205), the process proceeds to the first knock determination step (S101, S201). Thus, the control to increase the injection amount of the high octane fuel by a predetermined amount is repeatedly performed.
On the other hand, in another embodiment, the ECU 8 refers to a control map created by experiment or a control map created during operation, and the injection amount of the liquid mixture or the water contained in the liquid mixture according to the operation state Alternatively, the injection amount of the high octane fuel may be determined.
Thus, the present invention is not limited to the above-described embodiment, and can be implemented in various forms without departing from the spirit of the invention.

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Engine main body 3 ... Intake system 4 ... Exhaust system 21 ... 1st fuel injection valve 22 ... 1st fuel tank 40 ... Water tank 44 ... -Second fuel tank 52 ... second fuel injection valve

Claims (14)

An engine body (2) forming a combustion chamber (14);
A spark plug (17) for spark discharge in the combustion chamber;
An intake system (3) for introducing air into the combustion chamber through an intake passage (32);
An exhaust system (4) for exhausting exhaust gas from the combustion chamber through an exhaust passage (35);
A first fuel tank (22) for storing fuel;
A first fuel injection valve (21) for injecting fuel supplied from the first fuel tank into the intake passage or the combustion chamber;
A second fuel tank (44) for storing high-octane fuel having a higher octane number than the fuel stored in the first fuel tank;
A water tank (40) for storing water;
A second fuel injection valve (52) for injecting a mixed liquid obtained by mixing high octane fuel supplied from the second fuel tank and water supplied from the water tank into the intake passage or the combustion chamber. Internal combustion engine. An EGR passage (36) communicating the exhaust passage and the intake passage, and returning the exhaust gas flowing through the exhaust passage to the intake passage;
An EGR cooler (38) for cooling the exhaust gas flowing through the EGR passage,
The internal combustion engine according to claim 1, wherein water condensed from exhaust gas passing through the EGR cooler is supplied to the water tank. A rainwater collector (5) for collecting rainwater;
The internal combustion engine according to claim 1 or 2, wherein water collected by the rainwater collector is supplied to the water tank. An agitator (6) for mixing the high-octane fuel supplied from the second fuel tank and the water supplied from the water tank and supplying the mixed fuel to the second fuel injection valve;
A concentration sensor (51) for detecting the concentration of high-octane fuel or water in the mixture supplied from the agitator to the second fuel injection valve;
A control device that adjusts the amount of high octane fuel supplied from the second fuel tank to the stirrer and the amount of water supplied from the water tank to the stirrer based on the output signal of the concentration sensor. The internal combustion engine according to any one of claims 1 to 3, further comprising: 8). A knock sensor (16) for detecting vibration of the engine body, or an in-cylinder pressure sensor (18) for detecting an in-cylinder pressure;
The control device increases the injection amount of the liquid mixture injected from the second fuel injection valve or mixes the larger the knock of the internal combustion engine based on the output signal of the knock sensor or the in-cylinder pressure sensor. The internal combustion engine according to claim 4, wherein the ratio of water to high-octane fuel in the liquid is increased. A first fuel injection valve for injecting fuel into an intake passage or a combustion chamber, and a mixed liquid obtained by mixing high octane fuel having a higher octane number than the fuel injected from the first fuel injection valve and water into the intake passage or combustion In a control device for controlling an internal combustion engine provided with a second fuel injection valve for injecting into a chamber,
When knocking of the internal combustion engine is detected by an output signal of a knock sensor that detects vibration of the engine body or an in-cylinder pressure sensor that detects in-cylinder pressure, in addition to fuel injection from the first fuel injection valve, A control device for an internal combustion engine that performs control to inject a mixed liquid obtained by mixing high octane fuel and water from a second fuel injection valve.   Based on the output signal of the knock sensor or the in-cylinder pressure sensor, the larger the knocking of the internal combustion engine, the larger the injection amount of the liquid mixture injected from the second fuel injection valve, or the high octane fuel in the liquid mixture The control device for an internal combustion engine according to claim 6, wherein the ratio of water to the water is increased. When the combustion fluctuation rate obtained by dividing the standard deviation of the cylinder pressure in the combustion cycle of the predetermined period of the internal combustion engine by the average value of the cylinder pressure in the combustion cycle of the predetermined period is smaller than a third threshold (η), the second Increase the injection amount of the liquid mixture injected from the fuel injection valve or increase the concentration of water in the liquid mixture,
When the combustion fluctuation rate is larger than a third threshold value, an increase in the injection amount of the liquid mixture injected from the second fuel injection valve is prohibited, or an increase in the concentration of water in the liquid mixture is prohibited. Item 8. The control device for an internal combustion engine according to Item 6 or 7. When the internal combustion engine is in a warm-up state, control is performed to inject a mixed liquid of high octane fuel and water from the second fuel injection valve,
9. When the internal combustion engine is in a cold state, control is performed to inject high octane fuel from the second fuel injection valve instead of a mixed liquid of high octane fuel and water. The control apparatus for an internal combustion engine according to the item.   When the internal combustion engine is in a warm-up state and the remaining amount of high-octane fuel stored in the second fuel tank that supplies high-octane fuel to the second fuel injection valve becomes a predetermined amount or less, the high-octane number The control device for an internal combustion engine according to any one of claims 6 to 9, wherein control is performed to inject water from the second fuel injection valve instead of a mixed liquid of fuel and water.   When the internal combustion engine is in a warm-up state and the operation state of the internal combustion engine is in a low rotation high load region, water is injected from the second fuel injection valve instead of the mixed liquid of high octane fuel and water. The control device for an internal combustion engine according to any one of claims 6 to 10, wherein the control is performed. Knock determination step for determining whether the output signal of the knock sensor for detecting the vibration of the engine body or the output signal of the in-cylinder pressure sensor for detecting the in-cylinder pressure is greater than the first threshold value (α, δ) (S101, S201),
A warm-up determination step (S103, S203) for determining whether the temperature of the internal combustion engine is greater than a second threshold value (γ);
When the output signal of the knock sensor or the output signal of the in-cylinder pressure sensor is greater than a first threshold and the temperature of the internal combustion engine is greater than a second threshold, fuel is continuously injected from the first fuel injection valve. A liquid mixture increasing step (S104, S204) for increasing the injection quantity of the liquid mixture of the high octane fuel and water injected from the second fuel injection valve;
When the output signal of the knock sensor or the output signal of the in-cylinder pressure sensor is larger than a first threshold value and the temperature of the internal combustion engine is smaller than a second threshold value, the amount of high octane fuel included in the mixture is increased. An internal combustion engine control method including an octane number fuel increasing step (S105, S205). Combustion fluctuation for determining whether or not the combustion fluctuation rate obtained by dividing the standard deviation of the cylinder pressure in the combustion cycle of the predetermined period of the internal combustion engine by the average value of the cylinder pressure in the combustion cycle of the predetermined period is smaller than a third threshold value A determination step (S206);
When the combustion fluctuation rate is smaller than a third threshold value, a water amount increasing step (increase the injection amount of the mixed liquid injected from the second fuel injection valve or increase the ratio of water to the high octane fuel in the mixed liquid ( S207)
A water amount increase prohibiting step for prohibiting an increase in the injection amount of the liquid mixture injected from the second fuel injection valve or prohibiting an increase in the concentration of water in the liquid mixture when the combustion fluctuation rate is greater than a third threshold. The method of controlling an internal combustion engine according to claim 12, further comprising (S206; YES). Whether the amount of high octane fuel contained in the mixture injected from the second fuel injection valve exceeds a predetermined ratio (β) with respect to the injection amount of fuel injected from the first fuel injection valve Injection amount limit determination step (S102, S202) for determining
A high-octane fuel increase prohibiting step for prohibiting an increase in the high-octane fuel contained in the liquid mixture injected from the second fuel injection valve when the amount of the high-octane fuel contained in the liquid mixture exceeds a predetermined ratio ( The control method for an internal combustion engine according to claim 12 or 13, further comprising: S102; YES, S202; YES).

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